It is known that the current ISS water recovery and purification system is not closed-loop and, because of this, many resources are lost to waste. The current water recovery and purification system aboard the ISS is both open loop, meaning that it requires external inputs, and it is also inefficient. The current system works in two phases. The first phase is a Urine Processor Assembly (UPA) that processes the urine and flush water. The UPA first phase takes in 5.07 kg/day of inputted urine and flush H2O, and outputs 3.8 kg/day of non-potable H2O, which represents a loss of 25.0% of its input. This loss is waste in the form of a brine puck, which cannot be used in any capacity on the ISS, and is stored for later incineration and disposal. A brine puck is generated each time the UPA operates. Following the UPA in a second phase, a Water Processor Assembly (WPA) takes as inputs the non-potable water from the UPA as well as hygiene water, Sabatier water, and cabin condensate. These inputs total 9.1 kg/day. From these inputs, the WPA produces 7.7 kg/day of potable water. This means that every time the WPA operates, another 15.3% of the UPA output is lost. Additionally, the WPA system requires filter changes every few months and demands consumable oxygen for the system to operate.
Many inputs are lost to useless wastes in the current water purification system aboard the ISS. This system costs NASA money in restocking fees and does not provide a viable option for water purification and life support for future Mars applications with NASA's current propulsion systems. By creating a closed-loop water purification system where all inputs are turned into valuable outputs, NASA can move closer to achieving its goal of reaching Mars.
Another system that is being developed is referred to as an Alternative Water Processor (AWP), which is a part of NASA's “The Next Generation Life Support Project” as a candidate water-recovery system for long duration exploration missions. The goal of this project is to develop technologies that allow for spacecraft life support, in order to enable human presence beyond low Earth orbit. Specifically, the AWP is being developed to be a capable system for recycling wastewater from sources expected to be used in future exploration missions. The AWP is detailed in the paper “Alternative Water Processor Test Development.” Located at Johnson Space Center in the Advanced Water Recovery System Development Facility (AWRSDF), the AWP has two primary parts: a biological water processor (BWP) system and a forward osmosis secondary treatment system (FOST). The BWP system is made up of four Membrane Aerated Biological Reactors (MABR), which operate with oxygen as a consumable. Oxygen, a requirement for aerobic bacterial metabolism, must be supplied and resupplied to the system, which is something that does not work for a closed-loop system. The wastewater is biodegraded through nitrification/denitrification, which operates with oxygen. The MABR units were developed at Texas Tech University. A second part of the system is the FOST, which includes a forward osmosis (FO) membrane module and a reverse osmosis (RO) membrane module. These systems utilize membranes that are highly susceptible to fouling, which creates a consumable, and are inefficient purifiers of water. As a whole, the AWP is not an applicable option for long duration space travel, primarily due to its need for consumables. Additionally, this system does not produce valuable additional outputs like nutrients and clean gases.
An improved, higher efficiency system, where all inputs are converted into useful outputs, would be an asset, especially to NASA and its missions. Due to a loss of resources, the current system on the ISS, as well as the AWP, are not optimal for a manned mission to Mars based on current propulsion systems.
It would be beneficial to provide a new and improved sequence of primary water purification methods, combined with various secondary subsystems for use on space structures, such as the ISS, and to be applied towards further sustainable applications, such as for living on Mars. Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.